With the increase in personal electronic devices, HiFi audio is more popular than ever in many applications, such as smartphones, music players, home theaters, and even car infotainment. Many engineers and consumers devote themselves to the endless journey in HiFi audio. This document will help engineers understand, judge, design, and optimize a HiFi audio circuit.
An audio signal is a representation of sound—typically an electrical voltage. Audio signals usually have frequencies in the range of approximately 20 Hz to 20,000 Hz, which is audible to most humans. Audio signals may be synthesized directly or may be originated at a transducer, su ch as a microphone, musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal to sound.
High Fidelity or HiFi is a term used by home stereo listeners, audiophiles, and home audio enthusiasts to refer to high-quality reproduction of sound to distinguish it from the lower quality sound produced by inexpensive audio equipment. Ideally, high-fidelity equipment has inaudible noise and distortion, and a flat (neutral, uncolored) frequency response within the intended frequency range.
A sound system is mainly composed of the auditory system (human ears), hardware system (equipment), software system (signal source) and listening environment. The figure shows the typical block diagram of an audio reproduction hardware system, which converts the digital audio source to the voltage signal that drives the headphone. This article only focuses on this hardware system, which contains the DAC, current to voltage (I/V) trans-impedance amplifier, and difference amplifier.